Non-CPMG Multiband FSE for Improved SNR Efficiency on a Portable Low Field System

Motivation: Improve SNR efficiency of Fast Spin Echo on low field systems by leveraging the higher RF amplitudes and lower SAR limitations provided by lower field strengths. Goal(s): Perform multiband T2-weighted acquisitions with relaxed CPMG phase constraints. Approach: CPMG and non-CPMG multiband-4 pulses were designed by modulating Shinnar-Le Roux pulses with optimal multiband phases. Quadratic phase increment scheme was used to produce a stable non-CPMG echo train. Results: Non-CPMG artifacts were effectively eliminated using a quadratic phase increment scheme. Multiband-4 images had improved SNR compared to single-band images. Fast recovery improved CSF contrast but its intensity still differed with multiband due to shorter TRs. Impact: The application of multiband Fast Spin Echo (FSE) refocusing pulses that do not satisfy CPMG phase constraints was achieved using a quadratic phase increment scheme. Employing quadratic phase increment schemes may permit relaxation of other common FSE design constraints.